Nowadays, spring struts with pneumatic springs serve, in particular in passenger motor vehicles, as particularly comfortable suspension elements and ensure a pleasant driving feel in the case of a suspension arrangement which, depending on road conditions, can be adapted between “soft” and “hard” suspension characteristics. Here, a pneumatic spring system or ride-height control system is composed of the pneumatic spring struts, which comprise the pneumatic spring and damper units, for each wheel or at least for each axle, of the air supply system having a compressor, an accumulator and a regenerable dryer, and of further switchable or fixedly set pneumatic control elements, and for this purpose generally has an electronic controller.
The pneumatic spring struts in the prior art are, as is known, sensitive with respect to movements or deflections caused by transverse forces, that is to say by running gear forces normal to the axis of the pneumatic springs.
In particular in the case of relatively long pneumatic spring struts, acting transverse forces lead to a very slight but nevertheless measurable buckling movement wherein the shock-absorbing damper and rolling piston or rolling bellows are pivoted relative to one another. Here, if no precautions are implemented for compensating for such buckling movements, or if no corresponding guides are provided, such movements and forces can lead, within the components of the pneumatic spring strut, to increased frictional contact and thus increased wear. The design of the pneumatic spring struts must therefore be configured so that such movements can be compensated without transverse forces in the spring strut generating frictional wear on the components of the spring strut.
Solutions have already been disclosed in this regard in the prior art, for example by DE 195 08 980 C1, which is incorporated by reference. In the pneumatic spring strut presented therein, the housing, that is to say the damper cylinder of the shock-absorbing damper, has a collar which is welded thereto and to which the rolling piston, which is provided with a corresponding flange, is connected by means of an integrally vulcanized annular part composed of elastomeric material. The elastic ring permits a certain tumbling movement of the pneumatic spring piston relative to the damper cylinder, but without reducing to the desired extent the risk of increased frictional wear from buckling movements.
DE 199 08 607 B4, which is incorporated by reference, discloses a pneumatic suspension strut of the generic type in which the pneumatic spring cover has a concentric inner guide sleeve which interacts with a guide ring arranged on the bellows-side end of the pneumatic spring piston in order to support transverse forces. Here, however, the reduction or the absorption of buckling movements comes at the expense of an increased number of components.
As an additional effect, in the generic pneumatic spring struts in the prior art, the action of transverse forces leads, depending on dimensions and masses of the system, to vibrations and natural frequencies which are not only perceived as acoustically disturbing but can also adversely affect driving comfort.